This invention relates to semiconductor memory devices and more particularly to a substrate bias generator for a dynamic memory device of the type having a large number of internal clocks as associated with multiplexed row and column addresses.
As the sealing of MOS devices continues, second-order effects in basic MOS device operation are becoming more dominant in circuit performance. One of these second-order effects is the substrate current generated by impact ionization. This impact ionization current is a major portion of the substrate current which must be supplied for a clocked circuit, especially for a 256K dynamic RAM type of device, where the cell access is done through a clock sequence.
It is the principal object of this invention to provide an improved substrate bias generator for use in a dynamic RAM of the type having multiple clocks as associated with multiplexed row and column addresses, for example, particularly to prevent variation in voltage levels of the substrate bias with changing conditions of the internal clocks. Another object is to provide a substrate bias generator which supplies current associated with impact ionization for separate sequential clocks.